Sine wave shock tester



Dec. 15, 1953 o. E. SULLIVAN 2,662,392

'SINE WAVE SHOCK TESTER Filed Feb. 3, 1950 3 Sheets-Sheet l FlG.l.

22 o 22 ,/55 58 5a 59 I 59 s1 l'h lm I 2 46 4s 5 46 I: I5 57 27 u e 4s fl 5O 50 il m 42 39 I 11 mm 6 lm 2| [NW 9 :0 I I I no 8 DE. SULLIVAN Dec. 15-, 1953 D. E. SULLIVAN SINE WAVE SHOCK TESTER Filed Feb. 3, 1950 3 Sheets-Sheet 2 FIG.2.

Dec. 15, 1953 Filed Feb. 3, 1950 b. E. SULLIVAN 62,392

SINE WAVE SHOCK TESTER 3 Sheets-Sheet 5 DE. SULLIVAN i atented Dec. 15, 1953 UNITED STATES PATENT OFFICE SINE WAVE SHOCK TESTER Donal E. Sullivan, Washington, 15. 0'.

Application February 3, 1950, Serial No.- 142,245

6 Claims. (01. 73-12) (Granted under Title 35, U. S. Code (1952),

sec. 266) V invention relates generally to test devices and more particularly to shock testers of the type adapted to apply controlled acceleration shock to apparatusunder test for producing therein a Shock wave Sinusoidal in character.

The eirpense and delay inherent to field testingof ordnance materials and the difficulties incurred in controlling the many variables arising therefrom has led to extensive development of laboratory test apparatus suitable for applying to s'uch apparatus under test control shock conditions comparable in substantially every respect to those encountered by such a aratus in service use.

It has been found, however, that in order to effectively cover the wide range of laboratory shock applications required for testing the nunserous and distinctively difierent types of ordnance devices, several likewise distinctly different types of test apparatus must be provided, each form thereof being effective to produce in the test device certain of the shock effects more exactly corresponding to those to which the particular device is subjected during its use.

The shock tester of the present invention pro vides for producing in apparatus under test a shock wave of a particular pattern correspond iIig" to a Sine wave and wherein the character (if the wave pattern may be varied selectively by control-ling independenuy the eriod of aeceiera r tion and the rate of velocity change as applied to the particular part under test.

It is an object of the present invention to; provide a new and improved shock testing device adapted to prdduce an object under test a shock pattern sinusoidal in character.

lit is a further object of the present invention to provide a new and improved acceleration shock testing" device wherein a sinusoidal shook pattern produced theft-Eloy may be varied selectively by controlling independently the period of accelera tion and rate of velocity change as applied to the part under test.

'Gther objects and many of the attendant ad vantages of this invention will be readily appreciated as the same becomes better understood by referenceto the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. l is a front view in elevation of a preferred embodiment of the shock tester of the present invention; 7

Fig; 2 is a side View of the embodiment of the shock tester shown in Fig. 1;

Fig. 3 is a view partly in section and partly in 2 elevation through the latch assembly of the invention;

Fig. 4 is a graph showing an example of a sinusoidal shock pattern or shock wave produced by the tester.

The shock tester of the present inventidn is comprised of a frame structure generally desig rrate'd 5 and including an I-beam member 3 Vertioally supported from a base structure generally designated l and including a stand plate 8 se= cured as by welding to the forward face of the beam. A pair of angular brackets 9 are secured as by welding to plate 8 and are provided with suitable openings for receiving bolts H] for securing the frame to any suitable base support therefor.

Arranged adjacent the upper end of beam 5; Fig. 2, is a pair of horizontal plate members H secured as by welding to the side edges of the beam and arranged to extend forwardly there from for connectionwith a cross plate [2, Fig. 2, adapted to support from the ends thereof a pair of cylindrical-like member's l3 which preferably are welded or otherwise suitably secured thereto. Secured within the cylinders l3, as by nuts M,- 1s a pair of depending tension rod members l5 which are movably secured at their lower ends by springs I6. These springs extend between stop nuts [1 threaded with the lower ends of the rods and eyebolts l8 projecting upwardly from a forwardly extending plate It secured as by weld= ing to the forward face of the stand plate 8.

Rising from plate l9, to which it is secured as by nut 20, is a shaft section 2| arranged parallel to the beam 6, the upper end of the shaft being received within an opening provided therefor, but not shown, in a cross'plate 23 which preferably is welded at its ends to the plates ll respectively.

Movable vertically upon theshaft 2|, Fig. 2, is a bracket structure 2 t adapted for being secured in selected positions of adjustment upon the shaft as by clamp screws 25, the bracket includ= ing an annular housing-like portion 26- wherein is arranged an electro-magnet assembly 2? of which a part thereof projects outwardly from an opening provided therefor in the lower end of the housing;

The magnet 21 is admitted to the housing through an opening provided therein and now shown closed as by cap-piece 28 secured to the housing as by bolts 29. An electrical conductor cable 30 extending outwardly through an opening provided therefor in the cap-piece and thereafter passing to a control panel 3| by way of pu'l 3 leys 32, 33 and 34, is effective to supply current for energizing the electro-magnet 2! as a switch 36 on the panel 3| is closed.

Movable over the rods is a carriage structure generally designated 3'! and including a face plate portion 38 tapped and threaded at various positions thereon, not shown, for receiving therein the threaded end portions of rods 39 forming a part of a clamp assembly generally designated 40 and adapted, as nuts 4|, threaded with the upper ends of the rods, are tightened to draw downward a spanning plate 42 for pressing to the face of the carriage the part 43 to be tested.

Extending upwardly from the face of the carriage and preferably formed integral therewith is a pair of tubular guides 44 adapted to closely receive therein the rods l5 whereby the position of the face plate 38 of the carriage is maintained in a plane perpendicular to the rods as the carriage is moved vertically thereon, as will become more fully apparent as the description proceeds.

Secured to and preferably forming an integral part of the bracket structure 2-. is a pair of outwardly extending arm sections e5 wherein is secured as by nuts 8 a pair of depending rod members 4-? and 53 adapted for being loosely received within openings provided therefor, but not shown, within the carriage and plate mem bers 31 and I9 respectively, the rods moving vertically within these openings as adjustments are made in the position of the bracket 24 upon the shaft 2 i.

Secured to and extending upwardly from the base of the carriage is a pair of rod members 52 adapted to support thereon in spaced relation to the carriage a cross plate 5| whereon is secured in any suitable manner an annular plate 52 of magnetic material such, for example, as mild steel, and adapted as the carriage is lifted along the rods 27, 48, and 5 to engage the lower end of the magnet 22! and thereby, when the latter is energized, to magnetically connect with the magnet to support in an elevated position the carriage 37 above the stop nuts I! secured as indicated to the ends of the rods ii.

In order to effectively regulate the spring length of the rods 55 and thereby to accordingly regulate the particular shock pattern to be produced in the test part, sections of the rods I5 may be clamped to the beam 6, as by a bracket structure 55, in such a manner as to render a portion of the rods ineffective in response to the impact of the carriage 3'! upon the nuts I! and thereby to selectively alter the resilient character of the rods l5 and the characteristics of the sine wave illustrated in Fig. 4.

The bracket 55, provided for securing the rods to the beam E3, is comprised of a U-shaped member 56, Fig. 2, loosely arranged about the beam to connect as by welding to the rear face of an angular plate member 5'1 disposed against the forward face of the beam, the entire bracket assembly thereafter being clamped to the forward face of the beam by bolts 22 extending through a pair of a plurality of openings provided therefor in the beam. The heads of the bolts are drawn to the bracket to compress it to the forward face of the beam as by shoulder nuts which are arranged in the manner indicated in Fig. 2 for cooperation with the bolts 22.

The angular plate 5'. of the bracket is provided with outwardly extending arm sections SE to which plates 53 are secured as by bolts 55, for clamping the rods 5 to the crac'1et in an obvious manner as the bolts are tightened. In order that a more effective engagement may be had between the bracket 55 and rods 15, the rods l 5 may be threaded in any suitable manner for connecting with half round. threaded sections provided therefor, but not shown, within the forward face of the bracket and plate members 57 and 58 respectively, the threaded surfaces of the members interlocking to establish a gripping engagement therebetween.

With reference now to the operation of the device thus far described, it will first be understood that prior to the securing of the test part to the carriage 31, as by the clamping bracket 40, the desired characteristics of the shock to be applied to the test part is first determined and the position of the bracket 24 on shaft 2| and the length of the spring rods l5 are accordingly adjusted sufficiently, in the manner heretofore set forth, to provide the desired shock characteristics. After the proper securing of the test part of the carriage base, the carriage is thereupon lifted to the position for allowing the plate 52 supported thereon from the rods 50 to connect with the under face of the magnet 21 which is now energized by the closing of the switch 35.

The releasing of the carriage is accomplished by reversal of the polarity of the magnet 27, from the control panel 3|, it being understood that suitable apparatus, not shown, is contained therein for reversing the polarity upon manipulation of the switch 36. Polarity reversal preferably is provided in order to eliminate the restraining force due to residual magnetism in the magnet 21 and plate 52, thereby to obtain free fall of the carriage at the acceleration of gravity. The carriage is thus allowed to fall free of the magnet to accelerate downwardly along the tension rods I5 at a rate of velocity change predetermined for the particular test effects to be obtained.

As the carriage strikes the stop nuts l1, this being at a velocity controlled by the distance of free fall of the carriage, the spring rods l5 are momentarily elongated and thereafter contract to accelerate the carriage upwardly along the rods 41, 48 and [5. The carriage is secured at the crest of this rise by a latch assembly generally designated 61, Fig. 3.

The movement of the test part and carriage in the foregoing manner produces therein a shock wave corresponding to the sine curve shown in the graph of Fig. 4. The first half portion 62 of the curve indicates the rate of change in velocity or acceleration of the carriage during elongation of the rods, the velocity being zero at maximum elongation of the rods which condition is indicated at point 63 in the curve. The last half portion 64 of the curve represents the rate of change in velocity as the'rods [5 contract.

In order to prevent secondary shock by the carriage returning for a second time to the stop nuts ll, there is provided in the rod 41 a plurality of spaced notches 65, Fig. 3, adapted for being engaged by a plunger 66 forming a part of latch assembly generally designated '67 and secured as by screws 68 to the underface of the carriage plate 38. The plunger 6:5 is urged in the direction of the rod 41 by spring 69 arranged thereover and initially compressed between the base of a counterbore I5 and the plunger head ll. Orientaticn of the plunger 65 with respect to the notches $5 in the rod 41 is maintained by a stud screw 72 threaded with the under surceases face of the latch housing 13 and having the shank portion 80 thereof projecting upwardly into a notch keyway Bl formed in the undersurface of the plunger 65.

In order that interference with the rod 47 by the latch may be prevented during the interval of fall of the carriage following its release from the magnet 2?, the plunger 66 is initially main-- tained in a retracted position by engagement of a notch portion l4 therein with a second plunger 15. Plunger 75 has an inverted conical end portion i8 which cooperates with a similarly formed surface 82 of notch M to lock plunger 66 in the retracted position. This is accomplished by manual withdrawal of the plunger 66 followed by raising of plunger is into engagement with the notch 74 where it is retained by the urge of the spring 69 against the plunger 56'. Upon impact of the carriage with the nuts ll, the plunger 15, by reason of the weighted end portion Tl thereon, is accelerated downwardly by inertia to free the end portion l8 thereof from the notch M of plunger 66, thereby allowing the plunger 66 to be extended to connect with the rod el. Upon upward movement of the carriage responsive to contraction of the rods l5, the plunger 66, by reason of the inclined surface '59 thereon, is caused to skip the notches l5 to thereafter become seated in one of the notches as the upward motion of the carriage ceases, thereby to secure the carriage to the rod in an elevated position thereon and so prevent secondary shock effects being applied to the test part by the return of the carriage to the nuts ll.

From the foregoing, it will now be apparent that the aforedescribed apparatus is adapted to produce a shock wave similar to the sine curve illustrated in Fig. 4, it being understood that the particular period of acceleration and velocity change characteristics for a specific shock pattern desired being controlled or predetermined by the aforementioned adjustment, or combination of adjustments, of the apparatus. For example, in certain cases, vertical adjus ment of the magnet assembly only may be sufficient to provide the desired characteristics; in other cases a change in the effective length of rods it may be sufficient. In some cases, depending on the weight of the object under test, in addition to, or in lieu of, the foregoing adjustments, it may be necessary to add weight to the carriage and/or to change the diameter of rods. In any case, it will be understood that the elastic limit of the rods [5 must not be exceeded if the sine Wave characteristics of the shock pattern are to be developed and applied to the part under test.

Stated briefly in summary, the present invention contemplates a shock testing apparatus wherein the object under test is released for free fall at the acceleration of gravity through a distance sufficient to strike a yieldable energy storing means having a predetermined spring rate at a predetermined velocity whereby the object is decelerated downwardly at a predetermined rate of velocity change to a position of rest as the kinetic energy of the object is transferred to the storage means and thereafter is accelerated upwardly at a predetermined velocity change as the stored energy is released from the storage means, the rate of velocity change during the aforesaid downward and upward shock movements corresponding to a sine wave.

When the energy is released from the storage means, represented hereinbefore as the rods I5 for purposes of illustration, contraction of the 6 rods ceases whereupon the carriage and test part thereon move upwardly solely by the momentum thereof as the carriage moves away from the nuts ll, this point of separation being represented in the curve of Fig. 4 at point therein.

Obviously many modifications and variations of the present invention are possible in the lightof the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

The invention described herein maybe mantl factured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

l. A shock producing device of the character disclosed for imparting sine wave motion to an object under test comprising, in combination, a frame, a multiplicity of yieldable tension members depending vertically from a portion of said frame, stop means fixedly secured to the depending ends of said tension members, a carriage nor mally to come to rest on said stop means and movable on said tension members and adapted to support thereon an object to be tested, an electro-magnet arranged when energized to support said carriage in an elevated position on said tension m mbers, means for energizing and subsequently reversing the polarity of said electromagnet to respectively support and subsequently release said carriage for free accelerated motion thereof by gravity along said tensionmemhere into impact with said stop means whereby said tension members are yieldably extended and the reaction thereof accelerates said carriage upwardly on said tension members, thereby producing in said object a sinusoidal shock pattern, and means for latching said carriage at the peak of its rise on said tension members.

2. A shock applying device of the character disclosed for imparting sine wave motion to an object under test comprising, in combination, a frame structure, a pair of yieldable tension members depending vertically from a portion of said frame structure, stop members fixedly secured to the depending ends of said tension members, a carriage normally to come to rest on said stop members and slideably movable over said tension members and adapted to support thereon the part to be tested, means for securing said carriage in an elevated position on said tension members, means for releasing said carriage to accelerate by gravity along said members into impact with said stop members thereby to yieldably extend said tension members sufficiently so that subsequent contraction thereof accelerates said carriage vertically upward on said tension members in a manner to produce in the test part a sinusoidal shock wave having predetermined time-velocity change characteristics, and means for latching said carriage at the crest of its rise on said tension members.

3. A shock tester of the character disclosed for subjecting a part to be tested to a sinusoidal shock wave including, in combination, a frame, a multiplicity of yieldable tension members depending vertically from a portion of said frame, a plurality of stop members respectively secured to the depending ends of said tension members, a carriage normally to come to rest on said stop members and adapted to support thereon said part to be tested, means for suspending the cariiage above said stop members, means for releasing said carriage to allow the carriage and said part supported thereon to accelerate into yielding impact with said stop members thereby to extend said yieldable tension members to begin said sinusoidal shock wave upon said impact, said tension members having suflicient recoil to reverse the direction of acceleration of said carriage and part thereon and to cause accelerated upward movement thereof sufficient to produce in said test part a sinusoidal shock wave until said recoil is terminated, and means for arresting said carriage at the peak of the upward movement thereof.

4. A sine wave shock tester of the character disclosed comprising, in combination, a carriage adapted to support thereon a part to be shook tested, means including a frame for suspending said carriage in an elevated position, means for releasing said carriage to allow downward accelerated motion of said carriage responsive to gravity, a plurality of yieldable tension members depending vertically from said frame, a plurality of stop members secured respectively to the depending ends of said tension members and arranged to he engaged by said carriage for arresting the downward movement thereof and reversing the direction of acceleration of the carriage at the completion of its downward stroke, said tension members having suificient elasticity to impart predetermined sinusoidal velocity changes to the carriage and part thereon during the successive downward and upward movements thereof, and means for arresting motion of said carriage at the completion of its upward movement.

5. A shock testing device of the character disclosed for imparting sine wave motion to an object to be tested comprising, in combination, a support, a plurality of yieldable tension rod members vertically suspended from said support, stop means fixedly secured to the depending ends of said rod members, a carriage normally to come to rest on said stop means and disposed for vertical movement along said rods and having said object secured thereto for movement therewith,

means vertically adjustable for securing said carriage in an elevated position on said rods, means for releasing said carriage to allow accelerated motion thereof downwardly along said rod into impact with said stop means to momentarily elongate said rods and thereafter to accelerate said carriage vertically upward responsive to the contraction of said elongated rods, means for latching said carriage at the completion of its upward motion, and means for adjustably changing the effective length of said rods for controlling the characteristics of said sine wave motion applied to said test object and the carriage.

6. A shock testing device of the character disclosed for imparting sine wave motion to an object to be tested comprising, in combination, yieldable tension rod means dependingly arranged for elongation and contraction in a vertical plane in accordance with sine wave motion and having stop means at the lower ends thereof, means for releasably suspending the object above said stop means, means for releasing the object from said suspending means for free fall at the acceleration of gravity into engagement with said stop means whereby the tension rod means are yieldably elongated upon further fall of the object, said tension rod means having a spring rate sufficient to store the potential energy of said object therein whereby downward movement of the object is arrested upon predetermined elongation of the tension rod means and whereby the object is forced to rise thereby as said stored energy is released upon contraction of the tension rod means, and means for latching the object at the top of the rise thereof.

DONAL E. SULLIVAII.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,809,347 Martin June 9, 1931 1,985,478 Yuasa Dec. 25, 1934 2,115,841 Case May 3, 1938 2,496,298 Mackas Feb. 7, 1950 

